This invention relates to a method for installation of a cured in place liner by pulling in and inflating the liner and more particularly to a method of trenchless rehabilitation of an existing conduit by pulling a resin impregnated liner into the existing conduit everting an inflation bladder stored in a pressurized bladder canister into the liner by introducing air into the canister, isolating the canister and introducing continuous flow-through steam into the bladder without loss of pressure in the bladder and to the apparatuses for practicing the method.
It is generally well known that conduits or pipelines, particularly underground pipes, such as sanitary sewer pipes, storm sewer pipes, water lines and gas lines that are employed for conducting fluids frequently require repair due to fluid leakage. The leakage may be inward from the environment into the interior or conducting portion of the pipelines. Alternatively, the leakage may be outward from the conducting portion of the pipeline into the surrounding environment. In either case, it is desirable to avoid this leakage.
The leakage may be due to improper installation of the original pipe, or deterioration of the pipe itself due to normal aging or to the effects of conveying corrosive or abrasive material. Cracks at or near pipe joints may be due to environmental conditions such as earthquakes or the movement of large vehicles on the overhead surface or similar natural or man made vibrations, or other such causes. Regardless of the cause, such leakages are undesirable and may result in waste of the fluid being conveyed within the pipeline, or result in damage to the surrounding environment and possible creation of a dangerous public health hazard. If the leakage continues it can lead to structural failure of the existing conduit due to loss of soil and side support of the conduit.
Because of ever increasing labor and machinery costs, it is increasingly more difficult and less economical to repair underground pipes or portions that may be leaking by digging up and replacing the pipes. As a result, various methods had been devised for the in place repair or rehabilitation of existing pipelines. These new methods avoid the expense and hazard associated with digging up and replacing the pipes or pipe sections, as well as the significant inconvenience to the public. One of the most successful pipeline repair or trenchless rehabilitation processes that is currently in wide use is called the Insituform® Process. This Process is described in U.S. Pat. Nos. 4,009,063, 4,064,211 and 4,135,958, the contents of all of which are incorporated herein by reference.
In the standard practice of the Insituform Process an elongated flexible tubular liner of a felt fabric, foam or similar resin impregnable material with an outer impermeable coating that has been impregnated with a thermosetting curable resin is installed within the existing pipeline. Generally, the liner is installed utilizing an eversion process, as described in the later two identified Insituform patents. In the eversion process, radial pressure applied to the interior of an everted liner presses it against and into engagement with the inner surface of the pipeline. However, the Insituform Process is also practiced by pulling a resin impregnated liner into the conduit by a rope or cable and using a separate fluid impermeable inflation bladder or tube that is everted within the liner to cause the liner to cure against the inner wall of the existing pipeline. Such resin impregnated liners are generally referred to as “cured-in-place-pipes” or “CIPP liners” and the installation is referred to a CIPP installation.
The CIPP flexible tubular liners have an outer smooth layer of relatively flexible, substantially impermeable polymer coating the outside of the liner in its initial state. When everted, this impermeable layer ends up on the inside of the liner after the liner is everted during installation. As the flexible liner is installed in place within the pipeline, the pipeline is pressurized from within, preferably utilizing an eversion fluid, such as water or air to force the liner radially outwardly to engage and conform to the interior surface of the existing pipeline. Cure is initiated by introduction of hot water into the everted liner through a recirculation hose attached to the end of the everting liner. The resin impregnated into the impregnable material is then cured to form a hard, tight fitting rigid pipe lining within the existing pipeline. The new liner effectively seals any cracks and repairs any pipe section or pipe joint deterioration in order to prevent further leakage either into or out of the existing pipeline. The cured resin also serves to strengthen the existing pipeline wall so as to provide added structural support for the surrounding environment.
When tubular cured in place liners are installed by the pull in and inflate method, the liner is impregnated with resin in the same manner as the eversion process and positioned within the existing pipeline in a collapsed state. A downtube, inflation pipe or conduit having an elbow at the lower end typically is positioned within an existing manhole or access point and an everting bladder is passed through the downtube, opened up and cuffed back over the mouth of the horizontal portion of the elbow. The collapsed liner within the existing conduit is then positioned over and secured to the cuffed back end of the inflation bladder. An everting fluid, such as water, is then fed into the downtube and the water pressure causes the inflation bladder to push out of the horizontal portion of the elbow and cause the collapsed liner to expand against the interior surface of the existing conduit. The eversion of the inflation bladder continues until the bladder reaches and extends into the down stream manhole or second access point. At this time the liner pressed against the interior surface of the existing conduit is allow to cure. Cure is initiated by introduction of hot water into the inflation bladder which is circulated to cause the resin in the impregnated liner to cure.
After the resin in the liner cures, the inflation bladder may be removed or left in place in the cured liner. If the inflation bladder is to be left in place, the bladder will generally be one that has a relatively thin resin impregnable layer on the inside of the impermeable outer layer. In this case, the impregnable layer after eversion will cause the bladder to adhere to the resin impregnated layer of the liner as is well known in the art. At this time, entry into the manhole or access point is required to open the liner to release the water used to inflate the bladder and to cut off the ends extending into the manholes. When the inflation bladder is to be removed, it may be removed by pulling at the evasion end on a holdback rope attached to the trailing end of the inflation bladder used to control the speed of the eversion. This is generally done after puncturing the bladder at the receiving end to release the water used to evert the bladder and initiate the resin cure. Finally, the downtube can then be removed and service can be reconnected through the lined pipeline. If intersecting service connections are present, they would be reopened prior to resumption of service through the lined pipeline.
When a cured in place liner is installed using the pull in and inflate method, the outer impermeable layer of the liner remains pressed against the interior surface of the existing conduit. Certain advantages may be attained by this method of installation because the resin in the resin impregnable layer of the liner is trapped between two impermeable layers, namely the outer coating of the liner and the inflation bladder on the inside. Accordingly, there is little or no resin migration out of the resin impregnable layer of the liner. In a pull in and inflate installation, the liner coating need not be as strong as required in an installation by eversion, because the coating is not subjected to the pressure head required to evert the liner using the eversion process. Additionally, the coating does not come into contact with hot fluid circulating during the resin cure cycle. Thus, the liner may be of more uniform thickness in a pull in and inflate using an inflation bladder cured in place process compared to when the liner itself is everted.
While the pull in and inflate method has these advantages, the installation process is somewhat more complex than an eversion of the resin impregnated liner. Conventional pull in and inflate methods requires banding the inflation bladder to the downtube elbow and securing the collapsed liner already positioned in the existing pipeline to the downtube. This requires work within a restricted manhole space. Additionally, at the end of the installation, the inflation bladder may need to be removed after being cut at the distal end to release the water used as the inflation fluid.
While the pull in and inflate method utilizing water does have the various advantages noted above, the shortcomings tend to increase labor costs which are a significant aspect of the installation process. Accordingly, it is desirable to provide a rehabilitation method using pull in and inflate, wherein the liner is inflated with an eversion fluid, such as air, and the resin is cured by steam a heated curing fluid, such as flows through the inflated bladder, to take advantage of the energy available in the heated fluid to provide an installation method which is faster and more efficient economically than various rehabilitation methods currently practiced.